Image output devices that output images by forming dots on output media of various kinds, such as a printing medium or liquid crystal screen, are widely used as output devices of various kinds of imaging machines. Such image output devices handle images finely divided into tiny areas termed pixels, with dots being formed on the pixels. Where dots have been formed on pixels, viewed in terms of individual pixels, each pixel can of course only assume either a dot on state or a dot off state. However, viewed in terms of somewhat larger areas, it is possible for the density of the formed dots to be coarser or finer, and by means of varying this dot formation density, it is possible to output multi-value images.
For example, where dots of black ink are formed on printer paper, areas of fine dot density will appear darker, while conversely areas with dots formed more sparsely will appear brighter. Or, where luminescent spot dots are formed on a liquid crystal screen, areas of fine dot density will appear brighter, while areas with dots formed more sparsely will appear darker. Accordingly, through appropriate control of density of dot formation it is possible to output multiple tone images. Data for the purpose of controlling dot formation so as to give appropriate formation density in this way is created by subjecting an image to be output to prescribed image processing.
In recent years, there has arisen a need for such image output devices to be able to output images of higher picture quality and larger image size. With regard to meeting demand for higher picture quality, it is effective to divide images into finer pixels. By making pixels smaller, dots formed on pixels will not stand out as much, and picture quality can be improved thereby. Demand for larger image size is met by increasing the pixel count. Of course, while it would be possible to increase the size of the output image by making individual pixels larger, but since this could result in a decline in picture quality, the more effective way to meet demand for higher picture quality is to increase pixel count.
As the number of pixels making up an image increases, the time required for image processing becomes longer, making it difficult to output an image quickly. Accordingly, technologies enabling image processing to be executed faster have been proposed (JP-A-2002-185789).
However, even where image processing has been carried out rapidly, considerable time is required for transfer of the image data, or for transfer of the processed image data, and thus there are inherent limits in terms of the effect of making image output faster.
Another development seen in recent years is the desire to be able to supply output image data shot with a digital camera or the like directly to a printer or other image output device, to output images immediately. In such instances, image processing cannot be carried out using an image processing apparatus with high image processing capabilities, such as a personal computer. Consequently, it is necessary for image processing to be made simple, so as to enable execution thereof to be carried out by a digital camera or other image shooting device, or an image output device, or both.
With the foregoing in view, it is an object of the present invention to overcome the drawbacks of the prior art, to provide a simple image processing technology which would make it possible, while preserving sufficient output picture quality, to rapidly execute image processing and data transfer.